It is a documented fact that the performance of conventional two-electrode precipitators can be improved by pulse energization where high voltage pulses of suitable duration and repetition rate are superimposed on an operating DC-voltage.
For practical application, automatic control of any precipitator energization system is of major importance in order to secure optimum performance under changing operating conditions and to eliminate the need for supervision of the setting of the electrical parameters.
With conventional DC energization, commonly used control systems regulate precipitator voltage and current, and in general terms, the strategy is aimed at giving maximum voltage and current within the limits set by spark-over conditions. The possibilities of different strategies are extremely limited, since the precipitator voltage is the only parameter which can be regulated independently.
In contradistinction, pulse energization allows independent control of the following parameters:
1. DC Voltage level PA1 2. Pulse voltage level PA1 3. Pulse repetition frequency PA1 4. Pulse width PA1 (a) spark-over occuring during a pulse and causing a voltage drop of short duration; PA1 (b) spark-over occurring during a pulse and causing a voltage drop of long duration; PA1 (c) spark-over occurring between pulses and causing a voltage drop of long duration; PA1 (d) spark-over occurring between pulses and causing a voltage drop of short duration. PA1 Reduction of the DC-level by a certain predetermined amount and subsequently raising of it again; PA1 Reduction of the pulse repetition frequency by a certain amount and subsequently raising of it again; PA1 Reduction of the set value for the precipitator discharge current by a certain amount and subsequently raising of it again; PA1 Increase of the plateau voltage where the DC-voltage is controlled by using a periodically occuring plateau of increased voltage.
The possibility of combining the setting of several parameters enables development of highly efficient control strategies, if the phenomena taking place in the precipitator are measured and interpreted correctly.
I have invented a method of controlling these parameters to obtain an optimum operation of a pulse energized precipitator. More particularly, I have invented a method of controlling the pulse height in a manner to maintain the sum of the DC-voltage and the pulse height as high as possible, that is as high as it can be without causing an excessive number of spark-overs, when the DC-voltage is set or regulated to an optimal value.